In the generation of compressed air, and particularly in the oil-free generation of compressed air in rail vehicles, the compressor technology is subject to special requirements as a result of the large quantities of air that are to be generated and the extremely rough operating conditions. Complete operability must be assured even under rough environmental conditions (temperature, vibrations, shocks, etc.).
In the field of rail vehicles, oil-free spiral compressors are receiving ever more attention, especially in order to prevent the formation or accumulation of oil-containing condensate and in order to simplify the maintenance. Because the capacity of the compressors is to be greatly increased (for example suction volume flows of approximately 1600 1/min) in applications in rail vehicles, in comparison to the typical capacity of present conventional oil-free spiral compressors which are commercially available, and because of the subsequent high loads applied to the spiral compressor as a consequence thereof, it is not possible to simply enlarge such conventional compressors, especially in view of the very high axial forces which have the tendency to push the spirals of the compressor apart from one another. In so-called one-sided spiral arrangements, the support or counter bearing of such axial forces is particularly problematic, since very large bearings are required. These problems are increased in view of the required oil-free compression, due to which it is very difficult to remove or dissipate the frictional power or heat of the bearings. For the above mentioned reasons, compressors having a one-sided spiral arrangement have to date been regarded as not usable in the field of rail vehicles.
It is a further problem in such spiral compressors that the effort and complexity required for providing an "anti-rotation arrangement", which ensures the correct relative positioning of the two spirals, must be held as low as possible. According to the prior art, an Oldham-type coupling was generally used, but such a coupling is relatively unsuitable for larger units as well as for oil-free compressors. Conventional adjacent eccentric arrangements involve a considerable structural effort and complexity, especially in view of the great number of required bearings.